Rooney was forced to hop off the field after picking up an ankle injury in the build-up to the goal which gave Bayern a 2-1 win with the very last kick of the game at the Allianz Arena.

And although Bayern would certainly benefit were Rooney to be ruled out of the second leg next week, Van Gaal insists he would like to see the England striker back on his feet again as quickly as possible.

'I don't know whether Rooney is seriously injured but I think that Rooney is very important for Manchester United,' he said.

'He is their most important player and if you look at the statistics, then you see that Rooney has scored 31 goals.

'Rooney is so important for them and I hope for United that he is not seriously injured.'

Van Gaal knows as well as anybody how hard it is to compensate for losing such a crucial player having struggled during his first few months as Bayern coach without Franck Ribery.

The Frenchman was restricted to a handful of substitute appearances at the start of the season due to injury and Van Gaal was close to missing the opportunity of working with the winger as his own future hung in the balance after a disappointing start to the campaign.

But as Ribery worked his way back to fitness, the results started to arrive and Bayern and Ribery are now firing on all cylinders, as the French winger proved - equalising with a diverted free-kick after 77 minutes.

Star man: Ribery capped a fine display with the equalising goal against United

'It is incredible what Ribery did,' said Van Gaal. 'He, like Hamit Altintop and Danijel Pranjic, has not played much this season and now they have got to play at the highest level, and they did so.

'I could have left him out or I could have substituted him because he has had lots of injuries, but I think we now go to Schalke (at the weekend) without any injuries.'